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United States Patent |
5,687,192
|
Meyer
,   et al.
|
November 11, 1997
|
Circuit arrangement for transmitting information on a two-wire line
Abstract
In a two-wire line between a transmitter and a receiver, voltage or current
pulses are used to transmit information, the content of which is contained
in the period duration. This is achieved in that a transmitter connects or
disconnects the operating voltage for a receiver using a switch. It is not
necessary to have a digital-analog conversion or the reverse. Furthermore,
a high pulse-duty factor is used, so that the supplying of the receiver is
always guaranteed.
Inventors:
|
Meyer; Dieter (Feucht, DE);
Krockenberger; Klaus (Stein, DE);
Faber; Dieter (Reichenschwand, DE)
|
Assignee:
|
Robert Bosch GmbH (Stuttgart, DE)
|
Appl. No.:
|
311377 |
Filed:
|
September 23, 1994 |
Foreign Application Priority Data
| Sep 30, 1993[DE] | 43 33 358.3 |
Current U.S. Class: |
375/259; 375/257 |
Intern'l Class: |
H04L 027/00; H04L 025/00 |
Field of Search: |
375/22,36,238,257,295,296,300,259,237,239
327/291,103,130,31,34,35
341/189,143
329/312
|
References Cited
U.S. Patent Documents
4254403 | Mar., 1981 | Perez-Cavero | 340/310.
|
4353123 | Oct., 1982 | Rost | 367/137.
|
4399564 | Aug., 1983 | Cowen | 375/22.
|
4408185 | Oct., 1983 | Rasmussen | 340/310.
|
4419021 | Dec., 1983 | Terada | 374/101.
|
4896333 | Jan., 1990 | Can | 375/257.
|
4995054 | Feb., 1991 | Eckersley | 375/36.
|
5088112 | Feb., 1992 | Pyhalammi | 375/36.
|
5249201 | Sep., 1993 | Posner et al. | 375/295.
|
5264823 | Nov., 1993 | Stevens | 375/259.
|
Foreign Patent Documents |
2 083 301 | Mar., 1982 | GB.
| |
WO 92/06552 | Apr., 1992 | WO.
| |
Primary Examiner: Kuntz; Curtis
Assistant Examiner: Shankar; Vijay
Attorney, Agent or Firm: Kenyon & Kenyon
Claims
What is claimed is:
1. A circuit arrangement, comprising:
a transmitter;
a receiver;
a two-wire line coupled to said transmitter and said receiver;
said transmitter including means for generating one of voltage pulses and
current pulses by one of connecting and disconnecting an operating
voltage, said one of the voltage pulses and current pulses used to code
information using a preselected pulse-duty factor and to transmit said
information to said receiver via said two-wire line;
said receiver generating the operating voltage from said one of the voltage
pulses and current pulses, and decoding information.
2. The circuit arrangement according to claim 1, wherein said information
is coded by varying the pulse-duty factor.
3. The circuit arrangement according to claim 2, wherein the means for
generating said one of the voltage pulses and current pulses keeps the
pulse-duty factor constant independently of said information.
4. The circuit arrangement according to claim 2, wherein the pulse-duty
factor.gtoreq.50%.
5. The circuit arrangement according to claim 2, wherein the means for
generating said one of the voltage pulses and current pulses includes a
controller and a switch, said controller changing the operating voltage
for coding said information by controlling said switch.
6. The circuit arrangement according to claim 5, wherein said controller
includes a microprocessor.
7. The circuit arrangement according to claim 5, wherein said switch is a
semiconductor switch.
8. The circuit arrangement according to claim 1, wherein said receiver
includes means for generating the operating voltage, and a decoder for
decoding said information.
9. The circuit arrangement according to claim 8, wherein the means for
generating the operating voltage includes a stabilizer.
10. The circuit arrangement according to claim 8, wherein the means for
generating the operating voltage includes a controller.
11. The circuit arrangement according to claim 8, wherein said decoder
includes a microprocessor, said microprocessor being coupled to the
two-wire line for controlling a timing function.
Description
FIELD OF THE INVENTION
The present invention relates to a circuit arrangement for transmitting
information on a two-wire line between a transmitter and receiver.
BACKGROUND OF THE INVENTION
A circuit arrangement for transmitting a supply voltage and a control
signal, in which the power output element of a solenoid valve is triggered
via a double-conductor cable, is described in German Patent No. DE 37 17
260. On the transmission end, a microcomputer converts a digital control
signal for the power output element by means of pulse-width modulation
into an a.c. voltage, which is transmitted to the power output element. On
the receiving end, a rectifier, which extracts the operating voltage for
the power output element from the a.c. voltage, is connected to the power
output element. This is not a favorable solution, because the initially
available digital signal is converted prior to the transmission into an
analog signal. After the transmission, it is converted back into a digital
signal, to allow the solenoid valve to be digitally triggered.
SUMMARY OF THE INVENTION
An advantage of the circuit arrangement according to the present invention
is that no digital/analog conversion is necessary, but rather the control
information can be drawn directly from the period duration, or rather from
its frequency. Another advantage is that a very simple circuit arrangement
is achieved, since briefly interrupting the operating voltage being
applied to the two-wire line allows the information to be generated using
a simple semiconductor switch. In addition, the large pulse duty factor
has the advantage that considerable energy can be transferred via the
two-wire line, without the connected consumer being disturbed by the
short-term interruption of the operating voltage. Furthermore, since only
d.c.-voltage or d.c.-current pulses are transmitted, for the most part one
can use conventional integrated circuits, which place no especially high
demands on blocking protection. As a result, an inexpensive circuit design
is advantageously attained.
If only one parameter is changed and the other parameters remain constant,
the information can be easily coded and decoded.
Because the pulse duty factor is .gtoreq.50%, sufficient energy for
controlling the connected receiver or other device can also be
advantageously made available, so that one does not have to expect a power
surge or loss of data.
Since microprocessors are commercially available in large, inexpensive
quantities, they can be used, particularly in conjunction with a
semiconductor switch, to make a simple coding device. Microprocessors can
be easily programmed, so that programming changes are facilitated.
Decoding on the receiver side by means of a microprocessor also yields the
advantage that by making use of the integrated time functions, the
decoding of the information also becomes very simple. A connected display
device can, for example, still be easily triggered in the same way by the
microprocessor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 depicts a block diagram of the circuit arrangement according to the
present invention.
FIG. 2 shows a first voltage diagram according to the present invention
when no information is being transmitted.
FIG. 3 shows a second voltage diagram according to the present invention
when information is being transmitted.
DETAILED DESCRIPTION
Referring to FIG. 1, there is shown a transmitter 1, which is connected via
a two-wire line 4 to a remotely situated receiver 5. The two-wire line 4
can be designed, as needed, with respect to the information to be
transmitted. For example, it is possible to shield or twist the two-wire
line to shield it from outside influences. The transmitter 1 contains a
controller 2, which is preferably designed using a microprocessor. The
controller 2 is connected to a switch 3, which, for example, can be a
bipolar transistor or a field-effect transistor (FET). The switch 3 is
triggered by the control output of the controller 2, so that it connects
or disconnects the operating voltage U.
The receiver 5 has a voltage-stabilizing circuit 6, whose inputs are
connected to the two-wire line 4. Connected in parallel to the incoming
two-wire line 4 is a decoder 8, which decodes the information transmitted
as pulsed voltage or current pulses and delivers it to control-inputs of a
display 7.
The functioning of this circuit arrangement is described with reference to
FIGS. 2 and 3.
Referring now to FIG. 2, there is shown a voltage diagram, whose voltage
characteristic can be measured at the two-wire line 4. During normal
operation, when no information is being transmitted, the voltage is
measured as a constant voltage U.sub.1 on the two-wire line 4.
Referring now to FIG. 3, there is shown a voltage diagram of normal
operation when information is being transmitted by the transmitter 1. The
voltage U is likewise plotted over time t. However, the voltage U is no
longer a constant voltage U.sub.1, but rather is briefly interrupted for
short periods of time. A period duration T (frequency) results for each
pulse and each interval. In accordance with the exemplified embodiment of
FIG. 3, various period durations (frequencies) may be transmitted (for
example, T.sub.1, T.sub.2), depending on the information. On the
transmitting and the receiving sides, the coding is performed for the
corresponding period duration (frequency), for example, in accordance with
table 1. A specific function of the display may be controlled in this case
depending upon the period duration T. Table 1 reveals that when T=5.0 ms,
segment 1 of the display is switched on. When T=4.9 ms, segments 1 and 2
of the display are switched on, etc.
TABLE 1
______________________________________
T/ms Function
______________________________________
5.0 segment 1 on
4.9 segment 1, 2 on
4.8 seginent 1, 2, 3 on
4.7 segment 1, 2, 3, 4 on
______________________________________
The period duration is determined by the microprocessor which has a
free-running counter that counts up with a fixed time cycle.
If, for example, an external event is occurring, such as a high-low edge
transition at the input port, the current counter value is retained. If a
signal is applied to the input port, as shown in FIG. 3, then all counter
values, which are reached at the respective high-low edge, are retained.
By formulating the difference between two adjacent counter values, one can
then calculate the frequency f according to the formula f=1/T, where T=the
period duration.
To increase transmission reliability, the same period duration should be
transmitted at least three times. If all differential values are the same,
then the appropriate action can be initiated, such as energizing a display
or a loudspeaker. For example, the control 2 controls the switch 3 with
the period duration T. In this case, the operating voltage U is applied as
connected and disconnected voltage to the two-wire line 4. The receiver 5
generates its operating voltage, together with the voltage-stabilizing
circuit 6, so that the display 7, and/or another connected device,
receives a constant voltage.
As a decoder 8, for example, one can use a microprocessor. With the help of
the microprocessor's integrated time functions, for example, one can
determine the period duration T, or the frequency f.
In the same way, with the help of the microprocessor, one can trigger a
display, such as a liquid crystal display (LCD) liquid or crystal display,
and/or a signal transmitter, such as a loudspeaker, and in this manner,
output an optical and/or acoustic signal.
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